import numpy as np

def predict_action(state: np.ndarray):
    """
    基线策略：买入并持有 (Buy & Hold)
    输入:
        state: np.ndarray of shape (b, 32, 20)
    输出:
        action: np.ndarray of shape (b, 1)，恒为 1
    """
    b, l, c = state.shape
    assert l == 32 and c == 20

    # 始终买入并持有
    action = np.ones((b, 1), dtype=np.int32)

    return action
